The term "soapy substance" as used herein refers to a substance which is naturally retained in greasy animal hair and which can be extracted from the animal hair by using ethyl alcohol. The content of the soapy substance in the scoured animal hair can be determined by measuring the absolute dry weight of the scoured animal hair and the weight of the soapy substance extracted from the scoured animal hair with ethyl alcohol in accordance with a method set forth in paragraph 7, 8, 2, of Japanese Industrial Standard L 1022-1961, and is expressed by a ratio (in %) of the measured weight of the soapy substance to the absolute dry weight of the scoured animal hair.
The term "fatty substance" as used herein refers to a substance which is naturally retained in greasy animal hair and which can be extracted from the animal hair by using ethyl ether. The content of the fatty substance in the scoured animal hair can be determined by measuring the absolute dry weight of the scoured animal hair and the weight of the fatty substance extracted from the scoured animal hair by ethyl ether in accordance with the method set forth in paragraph 7, 8, 1 of Japanese Industrial Standard (JIS) L 1022-1961, and is expressed by a ratio (in % ) of the measured weight of the fatty substance to the absolute dry weight of the scoured animal hair.
It is known that greasy animal hair, such as greasy wool, is usually scoured with an aqueous scouring solution of a detergent, which contains a surface active agent and an alkali or alkaline salt, at an elevated temperature. This method is referred to hereinafter as a detergent-scouring method for animal hair. This detergent-scouring method is effective for eliminating not only the fatty substance, but also, the soapy substance from the animal hair material. However, this method is disadvantageous in the following points.
(1) Sometimes, the surface property and mechanical strength of the animal hair are deteriorated by the action of the alkali or alkaline salt in the scouring solution.
(2) Sometimes, the animal hair fibers are entangled with each other so as to form a felt during the scouring operation. (3) The scoured animal hair exhibits a decreased elasticity and stretchability. (4) The scoured animal hair exhibits poor carding and spinning properties. This feature causes the efficiency in production of animal hair yarn to be poor.
(5) A waste water having an extremely offensive door is discharged in a large amount from the scouring process, and causes the environment (rivers, lakes and seas) to be polluted therewith.
(6) The clarifying process for the discharged water waste is expensive.
(7) Consumption of heat energy is large.
It is also known that various approaches were looked into for eliminating the above-mentioned disadvantages of the detergent-scouring method. That is, the C.S.I.R.O. method (Wool Handbook, Interscience Publishers, Vol. II, Part 1 (1969) pages 71 through 74), Centri wool method (Wool Handbook, Vol. II, Part 1 (1969), pages 74 to 76), Sover method (Japanese Patent Application Publication (Kokoku) No. 38-10374) and a method of Japanese Patent Application Laid-open (Kokai) No. 53-74178, as well as a method disclosed in Textile Asia, pages 23 to 25 (September, 1971) used as organic solvent for scouring the greasy animal hair, especially, greasy wool.
This type of scouring method is referred to hereinafter as a solvent-scouring method. In the solvent-scouring method, the organic solvent is recovered from the scouring liquid waste. Therefore, substantially no scouring liquid is discharged from the solvent-scouring process. This feature results in substantially no environmental pollution.
However, the solvent scouring method has not yet been practically utilized in industry due to the following disadvantages.
(1) The effect of this method is unsatisfactory in the elimination of solid inorganic materials, for example, small particles of sand, and water-soluble substances from the greasy animal hair. This feature results in a poor brightness, and poor carding and spinning properties of the scoured animal hair. Also, the residual fatty substance is unevenly distributed on the surface of the animal hair. Therefore, in order to eliminate the above-mentioned disadvantages, it is necessary that the solvent-scouring process be followed by an additional washing process with hot water or an aqueous detergent solution for removing the solid inorganic particles from the scoured animal hair. This necessity causes the total cost of the preparation of scoured animal hair to be high.
(2) The effect of this method is excessive in the elimination of the fatty substance from the greasy animal hair. This feature causes the resultant scoured animal hair to exhibit a poor softness, a coarse touch and a poor adhering property of the hairs to each other.
A modified solvent-scouring method is disclosed by Japanese Patent Application Publication (Kokoku) No. 38-10374. In this method, a mass of greasy wool is opened, and the opened greasy wool is washed with water, and then, scoured with a non-alcohol type organic solvent. A combination of the above-mentioned washing and scouring operations is repeated twice or more, and an operation for scouring the animal hair with an alcohol is inserted between the combinations of the above-mentioned washing and scouring operations. However, this method is unsatisfactory in completely eliminating the disadvantages of the conventional solvent-scouring method, and exhibits the following additional disadvantages.
(1) The alcohol and water cause the soapy substance to be eliminated to a great extent from the animal hair, and the resultant animal hair exhibits poor carding and spinning properties.
(2) In order to carry out this method, large sized equipment is necessary. This equipment is extremely expensive.
(3) It is difficult and complicated to control the number of operations and the quality of the resultant product.
(4) The yield of the scoured animal hair by this method is poor.
Another modified solvent-scouring method is disclosed in Japanese Patent Application Laid-Open (Kokai) No. 53-74178. In this method, the greasy wool is scoured with an organic solvent and, then, washed with hot water. However, this method is disadvantageous in the fatty substance in greasy animal hair and the soapy substance is excessively eliminated by the organic solvent and by the hot water, respectively. This feature results in additionally decreased softness, decreased adhering property of the hairs to each other and decreased spinning property of the hair.
Under the above-mentioned circumstances, none of the known methods for scouring the greasy animal hair could suggest the best way of scouring animal hair.